Solar power is in the spotlight as concerns over global warming mount. Many European countries, especially Germany, as well as Japan and others have embraced solar technologies as a green alternative to fossil fuels.

Although Japanese companies are the world leaders in solar cell technologies, others are rushing to capitalize on the strong demand for such clean energy.

About 5 percent of Japanese households are equipped with solar panels. Raising that figure is key to the nation’s efforts to meet its greenhouse gas emissions reduction goal under the Japan-brokered Kyoto Protocol. Following are some questions and answers on solar power:

Where are solar cells found?

The power source for countless calculators, larger versions of solar cells can also be spotted glinting on roofs, where they gather the sun’s energy to help power household appliances.

New applications are being considered as larger-capacity photovoltaic cells that are more flexible, thinner and transparent gain usage.

Cars, vending machines and mobile phones can benefit from high-capacity cells, while clear, thin-film cells can be installed in windows instead of rooftops.

Electricity generated by solar panels can be stored in rechargeable batteries that are then plugged into electric cars.

In a disaster, the electricity stored in car batteries can be diverted for household use.

What kinds of solar cells have been developed?

Japanese solar cell manufacturers are aiming to develop more efficient and low-cost cells. One, made by placing thin layers of silicon on a glass substrate, uses only 1 percent of the silicon needed for conventional cells.

These thin-film cells are transparent and can be attached to windows without blocking out the sun.

Because it uses less silicon, this technology has drawn attention for cost reasons as well. Mainly used for semiconductors, silicon has risen in price in step with demand from solar cell makers.

Thus, Japanese makers also aim to develop cells that use metal compounds instead, including indium and selenium. Experts predict nonsilicon solar cells will reinvigorate the market for solar cell technology.

Is the need for solar power growing?

Yes. The emergence of new photovoltaic products, rising fuel costs and government assistance are encouraging widespread use of solar power and will lead to market expansion, according to Izumi Suda, an analyst at Yano Research Institute in Tokyo.

The market research firm said global solar power cell production, in terms of the total capacity of cells produced, is expected to expand more than threefold to 6.25 gigawatts in 2015 compared with 2005, led by Japan and European countries.

Who leads in solar power technology?

For seven years through 2006, Sharp Corp. was the world’s biggest solar cell producer. Japanese manufacturers, including Kyocera Corp., Sanyo Electric Co. and Mitsubishi Electric Corp., dominate the market with combined production that accounts for about 50 percent of global output.

However, Chinese and Taiwanese companies joined the top 10 for the first time in 2005.

Rather than go it alone, Japanese firms are tying up in response. In February, Osaka-based Sharp announced it had set up a joint venture with major semiconductor equipment maker Tokyo Electron Ltd. to develop equipment to manufacture thin-film solar cells. Rivals, including Germany’s Q-Cells, are competing to boost production capacity of solar cells as silicon supplies tighten.

What do Japanese companies need to do to lead the market?

“The first step is to raise the efficiency of the cells’ power generation so solar panels can be set up in smaller areas. Second is to lower costs,” said Suda of Yano Research Institute. “Electricity generated by a photovoltaic system is twice as expensive as conventional energy.”

She also noted that Japanese companies must secure enough solar cell materials, including rare metals that China and other countries are after as well.

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